From your description of the turbo eating itself at such low mileage and low speeds, it sounds as if the original owner may have been elderly and perhaps sticking to old habits had revved the the engine on shut down. Surely low speed is not harmful to a turbo, I thought the bores don't wear as well if they are run-in too gently. Anyway, apart from the huge disappointment from the breakdown, hopefully your 'new' engine and the ancillaries will run well.

Would that be elderly Sales Employees and various potential buyers taking the car out if it was a Dealership Demonstrators.?

 

?

Was the car a Dealership Demonstrator before being sold as a used car?